Start-stop regenerative telegraph repeater



Aug, 12, m2 F F x 2 2,252,622

START-STOP REGENERATIVE TELEGRAPH REPEA'I'ER Filed April 23, 1940 EWiaIaHh POLARIZED PM;

lNl ENTOR E M F GA A TTORNE Y Patented Aug. 12, 1941 START-STOP REGENERATIVEYTELEGR'APH REPEATER Francis H. Fox,..Detroit, Mich., .assignors'to Amerj ican Telephone and Telegraph Company, a

corporation of New York Application April 23,1940, Serial No. 331,251

9 Claims.

,This invention" relates to improvements in start-stop regenerative telegraph repeaters? and more particularly to arrangements for improvingthe operation of said repeaters in the presenceof intefering' impulses in the line circuit.

A mechanical. type of start-stop regenerator unithas been in extensive usefor some time in half-duplex telegraph repeaters, particularly in teletypewriter service.

Two" such regenerator The two ,regenerator units operate between two sections of a single line circuitan'd each section: may include a sensitivepolar receiving relay for control'of the associated receiving magnet. In apreferred form the locking arrangement referred to above is effective inpreventing one receiving relay from starting its associated, unit during the-reception of a signalseries by the other receiving relay and the locking circuit "for units are used in a repeater, one for transmis- 10 the inactive relay includes the'contacts of the stop in ne direction andthe other fortrans active relayandthe off-normal contacts of the mission in the'opp'osite direction. When the reactive unit: These contacts coope in lockpeater is" arranged for half-duplex operation, ing the inactive relay exceptfor a portion of that is,'for operation in oneidirection at a time, each S p pulse p g through the active side, provision is made for locking the inactive side t y permittingthe a ve Side 0 p d in'its stop position by means of cit-normal conto a'sig a such as a break S g r ts e tacts i n theunit operating in the active side ui dur ng-this unguar p so that'all impulses ofia signal series represent- A cu t arrangement of this type s b e ing a character will be sent before the other disclosed cflp pp cation for U. S. unit is permittedto operate; Patent Serial N0; fi ed byW. V. K. Large ,A regenerator unit." of the! type referred to is disclosed'in' U. S. Patent "2,105,173 issued to Zen nerbet 'al. on January 11; 1938, and reference may behadto this disclosurefor. details of its mechanisnrand operation.

The unit comprises, a receiving magnet, re-

sponsive to incoming fsignals, and transmitting contacts for, reproducing. the received signals and" retransmitting .them into the. outgoing 1 line circuit. An intervening, am mechanism, motorsynchronism with the incoming pulses, though somewhatdelayed with respect to them. 7 -A s-is we11 knofwn; thestart stop signals comprise a stop anda startimpulse and five, orsome-' times six; character-impulses: The stop pulse usually is amarking pulse n'd thestartlpulse isaspacingpulseg Fcr the purpose' of --maintaining successive out goingt signal series in isochrpnism with incoming signal series; the regeneration unit is equi ped witnastopmechanism adapted-to stop thecam' mechanism during the stop pulse and itorelease it. underi controlfof the receiving magnet in re sponse:toithe succeeding start pulse:

on April 16, 1936, which has issued as Patent No. 2,243,215 on May 27, 1941, and reference may be had particularly to Fig. 2- of that disclosure.

As is well known, interfering impulses usually termed-hits occur 'atyarying intervals in telegraph circuits of thistype and would be receivedin the repeater "circuit as a spacing impulse. It is'therefore general practice in commercial circuits to provide hitindicators that can beconnectedin each line section. These indicators may be offdiflerent types but have the commoncharacteristics of respondingseparatelyirr'all impulses passing in each direction in the line circuit'under observation and of giving-an indication, which may be visual, for each response. Thusan' observer wilLfind one meter in the indicator actively responding to a message in a given direction and another associated meter remaining inactive during the transmission of'the samemessage- Hits passing in the same di-rectionas the messagecannot be observed in this manner; whereas hits passing in the opposite :direction will give. readily observed indications on theinactive meter. In this manner too tems such. as those. just referred, to are disclosed.

in U; S. Patents 1,861,553 issued to R. B.-Shanck on June 7,.19 32,fand 1,982,022isS1-1ed to E. W. Reeve on. November 27, 1934..

It has,,however, been found that hits. arrivingin the sarn eY'riirection as the messagerat the repeater station and occurring, during-the un-. guarded portion of a stop pulse frequently give Other provisions are made in the commercial circuits for supervision of long spacing conditions, such as break signals. For this purpose it is important that the open condition remain uninterrupted by the repeater circuit.

It is therefore an object of the invention to prevent the reflection into the originating line of hits arriving on that line byastart-stop regenerative repeater circuit, so that line trouble may more quickly be located.

It is a more specific object to guard the inac tive side of a two-way repeater during the otherwise unguarded interval during the stop impulse to prevent false operation due to a hit.

It is anotherjspe'cific object to thus guard the inactive side'substantially without interferring with the normal modes of operation of the regenerative repeatercircuit.

In accordance with a feature of the invention the transmitting contacts of the regenerator unit are temporarily bridged by a bypass while the regenerator is in stop position;

In accordance with a more specific feature of the invention the by-pass is established by contacts closed by an off-normal cam on the regenerator unit in stop'position. I

'In accordance with another feature of the invention the bypass is established during each stop impulse of successive signal impulse series transmitted with about the normal speed of v operation and is made ineffective during a long operf'or spacing condition on the line'circui t extending byondthe length of one or more signal impulse series.

In accordance with a still more specific feature ofthe invention a timed relay, such as a slow-releasing relay, is made responsive to marking impulses fincoming' at least once for each signalimpuls'e'series .to keep its contacts closed for the completion of the by-passso thatd uring,

forjexam'pla a break'signal the contacts of the timing'relay' will open the by-pass' after a predetermined period equal to the length of one, two or. more signaling impulse series, thereupon maintaining the by''pass open and removing the tion with the attacheddrawing which shows a circuit diagram of a repeater station including two regenerator units of the general type shown in the Zenner et al5 patent referred to; above. The regenerator units are shown in diagrammatic form' with elementscorresponding to those of the device disclosed by Zenneret a1; and'nunibered to correspond to the numerals identifying the elements in'the'Zenner et al.patent.

It should, of course, be understood that whereas the embodiment shown in the drawing ineludes mechanical-regenerator units the inven'-' tion may. readily be adapted for operation with other types of start-stop regenerator units, such as the well-known type using segments and brush contacts. It should further be understood that whereas the disclosed embodiment includes a circuit arrangement similar to that of Fig. 2 in the copending application by Large referred to above, other circuit arrangements such as that shown in Fig. 1 or 3 of the Large disclosure may be used for the purposes of the invention.

Referring now to the circuit diagram shown inthe drawing the system comprises a repeating station with relay equipment for half-duplex operation between two line sections LW and LE which may terminate in subscribers loop circuits including the usual receiving and transmitting equipment at each subscribers station.

The repeating station comprises two regenerator units 2| and 292, one for each direction of transmission. Two polar relays 203 and 204 having operating and biasing windings are associated with the regenerator units 2M and 232, respectively. The loop circuits will normally be closed and the normal line current will act to operate relays 2G3 and 294 to marking. A spacing signal is transmitted by opening either one of the loop circuits which causes the relays 293 or 24 to be operated to spacing by their'biasing windings which are normally connected to a predetermined potential through potentiometers 2H and 2l2, respectively.

Each regenerator unit will be assumed to be of the type disclosed in the patent to Zenner et al. referred to above and comprises a receiving magnet M controlled, by its associated receiving relay, transmitting contacts T controlled by the magnet M andby the cam mechanism of th unit for operation into marking or spacing positions, and off-normal or locking contacts L controlled by the cam mechanism.

The transmitting contacts T are included directly, in the respective'line circuits and thus repeat the signals directly into the subscribers loops," the outgoing impulses passing through the operating winding of the'receiving relay in the outgoing circuit and tending to operate that relay., The polar relays are, however, prevented from responding to outgoing signals, except for short intervals during eachstop condition, by the application of a locking potential to the potentiometer connected to the biasing winding of the relay, the locking potential being applied either from'the' spacing contact of the active polar relay or from the locking contact of the active regenerator unit or both, this locking potential is of a polarity opPQsite to that permanently applied to the other end of the potentiometer.

Referring now particularly to the details of each regenerator unit, the cams 2!, 22, 23, 24 are mounted on a common cam sleeve 20 driven through a friction clutch 3| by any suitable powersupply P. J The stop cam 2| cooperates with a stop latch 34 for stopping-the cam sleeve in stop position; the stop latch 34 is in turn controlled by armature {l0 ofmagnet M so that when the armature 40 is' released .by magnet M the latched will permit the stop cam 2| to rotate.

The'armature 40 has a spring 55 for retracting thearmature and the magnet M is not of asuifi- .cient strength duringia marking pulse to attract the armature, but is of "sufficient strength to hold the [armature attracted during the marking pulses. 'lfl eyarmature 40 cooperates with a flutter cam 22 with projections properly distributed about its periphery for raising the armature 40 against the spring 55 to present the armature to the*mag net -If}a-t sucl i time magnetis energized, as during-amarking pulse,- the -armature Ill-remains attracted. ;If; howeventhe mag net is deenergized thearmature Will'be retracted after the passing ofthe cam projectionon cam 22: I The=- armature 40 also "carriesa contact operating member 65; schematically shown as being-flexible so -that:the member 65 'maybelocked against either the markingcontact m or the-spacing-contactls by means of locking lever 'I'I' while thearmature 40 is in either position.

Thu-s when the-armature is attracted-it will exert a-torce on the flexible arm 65- in the directionoi the marking contact and when it is retracted it w ill exert-a force on the arm 65 in the direction of a spacingrcontact. These forces exerted bythe armature: 40 will, however, notbe eiiective until the arm- 65 is released' by thelocking lever TI which forms part of the-1ock-arm:51. The lock. arm 51 is normallyin engagement with a loclc cam -24 b y means ot a spring- 81- and during rotation: of the cam-sleeve will be raised at predetermined intervals by the projections on the lock cam 24, thereby-removing the locking-lever I 'l'l from engagement withthe flexible-contact arm 65'land permitting the latter.- to swing into engagementawith either the marking orthe spacing. contact asdetermined by the position of the armature. 49. The distribution of the projections onthe flutter cam 22.. andlock cam 24 is-such thatifor any particular impulseof asignal impulse seriesrsthe. armaturei 40+wi11- first be presented, to.themagneteMmand-will be held or droppeditb'yr: the. magnet,..=as= the .case may .be,.

whereuponthe .lock:arm..-5'I will be operated to permit. .the flexible contactearm;65 to, if necessary, .change from one .position. tothe other.

-An-iioff;normal cam 23 has a single projection Whidhiil'l? stop position operates. the .locking lever liflaagainst'thetensiorr of a contact spring to open I thezlocking contacts L,-.ther.eby,opening the hold-v ing; circuit forthepolar relay connected in the output circuit of the unit. i 1

For; purposesof theinventiona pair of contacts I23 and 124 are added to the locking contacts'li of the respectivegunits 20] and 222 and slow -releasing. relays. I2I and I22 have their I windings connected in theoperating'circuit of the respectiveqregenerator magnets M and have. their contacts seriallyconnectedwith thev auxiliaryy contacts. I23 and [24,.respectively, in a eta) by -pass ior the-transmitting,contacts T of. the;

regenerator, asashown in the drawing. 1 Thus the slow-release relay IZI, for example, willoperate in response to the polarrelay 203 in marking position and the slow-releaseactionof relay I2I LW through the operating' winding ofrelay 203 and over the closed contacts T of the regenerator unit 202. Relay 203 responds. bymoving'to spacing, thereby reducingthe currentin magnet M of the unit 2M and relay I2'I 'to zero and also applying negative potential to the low resistance end ofthe potentiometer, 212, the high resistance end of which is connected to positive" j potential, and theleb'y reversing thmufleiibin thebiasingf winding oi relay 204 to 1101s this relay in marking position. The unit 2M willbe startedby the release of armature 401and im-- mediately thereafter the lockingcontacts L will :be-operated to their alternate position thereby applying negative potential to the potentiometer 2I2 and thus preventing relay 2M and unit 202' from operating until unit 201 again reaches its stop position.

After a short interval the lock arm 51. is elevated by the first projectionon cam24 to unlock the flexible contact arm 65 which quickly moves to spacing positiondue to the stored-up tension produced by thearmature when the lat ter was dropped. The transmitting contacts T- thus will be opened and will transmit a spacing.

signal into the loop LE without affecting relay 204. V 1

The circuitwill remain in this condition until a marking impulse is received over loop LY which will operate relay 203 to marking thereby energizing magnet M of unit 20'I. However, as the cam sleeve revolves the flutter cam 22. will raise the armature 4|]. oncefor. each impulse period. .thereby presenting the armature to. themagnet.

M for holding or dropping after. eachcam projection has passed. Cam 24 raises the lock arm 51 once foreach impulse period shortly after the armature has been presented'and has assumedv its position in accordance with the characteristic Thus the transmitting contactsT of the pulse. are permitted to open orclose'the line circuit LE in accordance with theposition of armature 40, thereby transmitting impulses from LW into the outgoing circuit LE.

When the stop impulse arrives, relay 203 moves to marking thereby energizing magnet M of unit 20I and relay I2I.

net the armature will be held attracted, thereby placing the 5130132131101! 34 in the path of the cam 2I forstopping the'unit. Shortly thereafter the; stop projection oncam24 releases the transmitting contacts T which then moveto marking, or remainin marking as thecase may be, for transmission of a stoppulse into theloop circuit LE. ,Thecontacts T will-thereafter be locked while the unit mloves tostop position and until the unit is againstarted, whereupon the start projection of cam. 24 again will release the con-- tacts T. The circuit is thus restoredto normal;

condition as shown in the drawing.

It will be notedthat the negative guard potential applied by relay 203 to potentiometer. 2I2 'is disconnectedduringthe entire length of the incoming stop pulse and that the negative guard potential applied by locking contact L of unit ZGI to the potentiometer 212 isdisconneoted by the off-normal cam 23 foran interval'from about the beginning of the outgoing stop pulse until shortly after the next starting of the unit. Relay 28 i therefore is permitted to operate to spacing from I the moment off-normal cam 23 opens the locking contacts L until the moment-when relay 2E3op crates to spacing in response to the next start pulse. permit a break signal from line. LE to start the regenerator unit 202 for placing along opening on the line circuit LW, thereby notifying the transmitting subscriber that the other party wishesto out in.

The auxiliary off-normal contacts" I23'on the unit 20-I aread-justedto close-shortly before contacts L are 'openedby off norma'l cam" 23 and to again open shortlyaitertlie" contacts are'closed" .When the stop projection. of cam 22 next presents the. armature to the mag- This unguarded interval is provided to' upon starting of the unit. With slow-releasing relay |2I holding its contacts closed'during normal transmission, the by-pass for contacts T thus will be closed for an interval slightly longer than that in which the locking contacts are open during the stop pulse, and thus will be established during the entire unguarded period referred to above. The purpose of this provision will be explained below.

In the case of a break signal being transmitted from line west to the unit 251! this unit will be started and will keep on rotating so long as the spacing condition of the break signal is maintained and the slow relay l2! will open the bypass after the absence of one or'two stop impulses, dependent upon the timing adjustment of the relay, thereby removing the artificial markipg condition imposed on the line LE by the bypas each time the off-normal cam 23 closes the auxiliary contacts I23 and thus permitting a continuous break signal to be transmitted over line LE after the unit has revolved once or twice. The removal of the bypass thus permits the proper operation of the supervisory equipment referred to above and the proper reception of the break signal in loop LE. As is well known, the break signal may be sent during transmission in the opposite direction as a request to the other station to stop sending, or a similar spacing signal may be sent over an idle line to call or start the other station.

When a hit occurs on line circuit LW during transmission from line LW to line LE, as described above, a spacing condition will be imposed on the incoming end of line circuit LW causing relay 203 to operate to spacing for the duration of the hit, and the magnet M of the rotating unit 21' will drop the armature each time it is presented during the hit and will cause corresponding spacing pulses to be transmitted into the line LE. Such hits may interfere with the message in line LE but cannot be observed on the hit meter for either the active or inactive direction. A hit on line LE occurring during transmission from line LW may also interfere with the reception of the message in line LE but can be properly observed on the inactive hit meter associated with the line circuit.

A special condition arises, however, when a hit occurs on, the incoming circuit during a stop pulse and particularly when the hit is present at the time the transmitting contactsT are unlocked for operation to marking in response to the stop pulse.

Relay 233 thus will be operated to spacing by the hit on line LW thereby causing the magnet M to drop armature 40 after it has been presented by the stop projection on cam 22 with the result that the transmitting contacts T, when released by locking cam 24, will move to spacing instead of moving to marking as in the case of an uninterrupted incoming stop pulse. The unit 2M will thus fail to stop and the contacts T will remain in spacing during the subsequent start pulse and at least until the armature has been presented to magnet M by a projection on cam 22. If the hit be long enough to last into the incoming start pulse, the receiving relay 203 would remain in spacing and there would be no unguarded period for relay 204 which thus would remain locked by contacts L of unit until the next stop pulse from line LW. However, if the hit should cease before the beginning of the incoming start pulse, the unguarded period for relay 204 may be as long as during normal operation.

, a time to repeat start-stop code impulses incom- In the absence of the by-pass, provided in accordance with the invention and described above, the opening, due to the hit, of the line circuit LE 'by contacts T of unit 20l during the unguarded interval of the stop period, 1. e., after the passing of the hit when relay 203 has returned to marking would cause relay 204 to move to spacing and to start its associated regenerator unit 202. A guard potential would immediately be applied to potentiometer 2H for locking relay 203 in marking position during a revolution of unit 202, and when the transmitting contacts of unit 202 were released by the start projection on cam 24 a spacing pulse would be transmitted into line circuit LW. Since transmission from line LW would continue the spacing pulse from unit 202 against the prevailing direction of transmission would be indicated on the hit indicator as a hit originating in line circuit LE, which would be erroneous.

With the by-pass for transmitting contacts T provided in accordance with the invention, the erroneous hit indication under the special condition just described is prevented, and the location of line faults is expedited.

Thus when a hit occurs on line LW and is present when the transmitting contacts T of unit 2! are unlocked by the stop projection on cam 24 these contacts will be locked in spacing as described above, but the line circuit LE will remain closed over the by-pass including the auxiliary off-normal contacts I23 and the contacts of slow-release relay I2l in series. Since this by-pass, as already described, is closed during the entire unguarded interval of the stop pulse, relay 2B4 remains unaffected by the hit and a false start of the unit 202 is prevented; thus the inactive meter in the hit indicator remains unaffected by the hit in the active direction. However, since armature 40 of unit 20| remains retracted due to the hit, the cam sleeve will fail to stop and there may be some interference with the transmission of one or two characters to the loop circuit LE.

Inasmuch as the two generator units of the repeater station are similarly connected into the circuit, operation of the system during transmission from'the line LE to the line LW will proceed in the same manner as described above for transmission in the opposite direction. Also 'the'prevention of a false indication by the hit meters due to a hit on line LE during a stop impulse is accomplished in the same manner as described above for a similar hit on the line circuit LW.

Whereas the invention has been described above as being applied to a circuit arrangement in which the receiving relay in the inactive side is locked against operation except during the unguarded period, it should be understood that the invention is readily adaptable to a circuit arrangement in which the starting of the inactive unit is prevented, except during the unguarded period, by the application of a guard potential or other provision effective during the revolution of the active unit in locking the inactive magnet. Examples of such systems are shown injFigs. 1 and 3 in the application by Large referred to above.

What is claimed is:

l. A two-way start-stop telegraph repeater circuit connectedbetween two line circuits and comprising a west and an east regenerative repeater alternately active and inactive one at ing from west and east into the east and west line circuits, respectively, each of said repeaters including receiving winding means, timed repeating contact means controlled as to code by said receiving winding means, oif-normal guard contact means connected to lock the other of said repeaters against operation during the operating cycle of the active repeater except for an unguarded period during the stop condition of said active repeater, and auxiliary off-normal contact means connected to prevent the said other repeater from operating in response to a false start impulse by said repeating contact means of the active repeater during said unguarded period.

2. A repeater circuit in accordance with claim 1 in which said auxiliary off-normal contact means of each repeater is connected to shortcircuit the associated said repeating contact means during the said unguarded period.

3. A repeater circuit in" accordance with claim 1 in which each repeater further includes slowacting relay means responsive to stop impulses for rendering said auxiliary contact means effective during substantially continuous character transmission by said repeater and for rendering said auxiliary contact means ineffective during intervals between stop impulses of substantially greater duration than that of a character impulse series.

4. A two-way start-stop telegraph repeater circuit comprising two regenerative repeaters a1- ternately active and inactive for transmission in opposite directions one at a time, each of said repeaters including receiving winlding means, timed repeating contacts controlled as to code by said receiving winding means, ofi-normal guard contacts connected to lock the inactive repeater against operation during the operating cycle of the active repeater except during an unguarded period during the stop condition of the active repeater, and auxiliary off-normal contacts connected to short-circuit the associated repeating contacts during substantially the total duration of said unguarded period.

5. A repeater circuit in accordance with claim 4. in which each of said repeaters further includes a slow releasing relay having contacts serially connected with said auxiliary contacts and being responsive to successive stop impulses transmitted at substantially normal intervals to close its contacts for completion of the said short circuit and to hold its contacts closed during said intervals and being timed to release during intervals between stop impulses substantially longer than normal to open its contacts for opening of said short circuit.

6. A two-way start-stop telegraph repeater circuit connected between two line circuits and comprising a west and an east regenerative repeater alternately active and inactive to one at a time repeat start-stop code impulses incoming from west and east into the east and west line circuits, respectively, each of said repeaters including receiving winding means, timed repeating contact means controlled as to code by said receiving winding means, off-normal guard contact means connected to lock the other of said repeaters against operation during the operating cycle of the active repeater except for an unguarded period during the stop condition of said active repeater, and circuit means including contact means normally closed during said stop condition and connected to said other repeater for, when closed, preventing the said other repeater from operating in response to a false start impulse by said repeating contact means of the active repeater during said unguarded period.

7. A two-way start-stop telegraph repeater circuit connected between two line circuits and comprising a west and an east regenerative repeater alternately active and inactive to one at a time repeat start-stop code impulses in"- coming from west and east into the east and West line circuits, respectively, each of said repeaters including receiving winding means, timed repeating contact means controlled as to code by said receiving winding means, guard contact means connected to lock the other of said repeaters against operation during the operating cycle of the active repeater except for an unguarded period during the stop condition 01 said active repeater, and circuit means including additional contact means and connected to said other repeater to lock said other repeater against operation during a starting impulse produced by said repeating contact means of the active repeater in the stop condition.

8. A two-way start-stop telegraph repeater circuit connected between two line circuits and comprising a west and an east regenerative repeater alternately active and inactive to one at a time repeat start-stop code impulses incoming from west and east into the east and west line circuits, respectively, each of said repeaters including receiving winding means, timed repeating contact means controlled as to code by said receiving winding means, guard contact means connected to lock the other of said repeaters "against operation during the operating cycle of the active repeater except for an unguarded period during the stop condition of said active repeater, and circuit means including slow acting contact means and connected to said other repeater to lock said other repeater against operation during a start condition efiected by said repeating contact means of the active repeater in stop condition and adjusted to after a predetermined interval restore said other repeater to normal operating condition.

9. A two-way start-stop telegraph repeater circuit connected between two line circuits and comprising a west and an east regenerative repeater alternately active and inactive to one at a time repeat start-stop code impulses incoming from west and east into the east and w est line circuits, respectively, each of said repeaters having an operating circuit adapted to be opened for starting of said repeater in response to a starting impulse and further including receiving winding means, timed repeating contact means controlled as to code by said receiving winding means, guard contact means connected to lock the other of said repeaters against operation during the operating cycle of the active repeater except for an unguarded period during the stop condition of said active repeater, and circuit means including additional contact means connected to maintain closed the operating circuit for said other repeater during a start condition effected by said repeating contact means of the active repeater in the stop condition and adjusted to after a predetermined interval restore said operating circuit for normal starting of said other repeater.

' FRANCIS H. FOX. 

